Sewing machine



H. F. BRIGGS ET AL SEWING MACHINE Filed Dec. 12, 1934 2 Sheets-Sheet 1 5 R a Y o a E T /D M NR E50 0 WE n n 1 N A N7 u n WM m May 4,1937.

H. F..BRIGGS ET AL SEWING MACHINE Filed Dec. 112, 1954 2Sheets-Sheet 2 onw INVENTOR HOWLH/VD E 52/665 ROBEFW N CU/VDHLL "lATTORN Patented May 4, 1937 UNITED STATES PATENT OFFICE 2,079,002 SEWING MLACHlNE Application December 12, 1934., Serial No. 757,080

19 Claims. (01. 112-200) Our present invention relates to an improve ment in the looper mechanism associated with aheavy duty sewing machine particularly adapted'for closing the mouths of large, multi-ply paper bags after they have been filled with a quantity of material. Such bags are usually made of fromthree to five plies of smooth, stiff, kraft paper. The bags are usually formed with gussetted sides so that at the side edges of the bags there may be as many as twenty plies of material. The mechanism for sewing through such a large quantity of kraft paper must be rigid and strong without sacrificing accuracy and fineness of operation. Ourpresent invention achieves both objects to a marked extent, enabling the bag mouths to be closedwith a tightly drawn, accurate stitch and reducing the possibility of dropping stitches to an absolute minimum.

Our invention constitutes a portion of the mechanism of a double-thread, interlocked, stitching machine and comprises an improvement upon the'mechanism of the pending application of Howland F. Briggs, Serial No. 690,053, filed September 19, 1933, (now Patent No. 2,043,149 granted June 2, 1936) to which reference may be made for other portions of the mechanism which are not fully described herein;

Referring to the drawings wherein like numerals referto like parts throughout:

Fig. l is a side elevation of. a sewing machine, the front cover of which has been removed and portions broken away in order to clearly view the portion of the apparatus constituting our present invention; g

Fig; 2 is a section of Fig. 1 taken along line 2-2and looking in the direction of the arrows;

Fig.3 is a section of Fig. 1 taken along line 3-3 of Fig. 1 and looking inthe direction of the arrows;

Fig. 4 is a schematic representation of a sewing machineembodying our invention and indicating the manner of leading the threads to the needle and thelooper;

Fig. 5is a motion study of our improved looper mechanism taken in the plane of Fig. 1 and showing the vertical component of motion of various parts as will be more fully explained hereafter;

Fig. 6 is a motion study of the same parts taken at right angles to Fig. 5, or projected onto'a vertical plane; and

Fig. 7 is a further diagrammatic study.

The machine comprises a frame I, having a throat 2 through which the material may pass, being guided between a presser foot 3 and aperforated throat plate 4 through which the feed dog 5 may operate. The various portions of the mechanism are operated by a shaft 6 having eccentrics mounted thereon. Of these eccentrics, the one marked 1 operates a needle bar 8 carrying a needle 9 through which the needle thread 5 6 is passed. Eccentric II and eccentric I2 operate the feed dog 5 in" the manner more fully, described in the copending application of Robert N. Cundall and Lincoln A. Cundall, Serial No. 690,988, filed September 26, 1933 (now Patent No. 2,043,094, granted June 2, 1936). It will be appreciated that the feed dog and needle bar may be operated in other manners, but the foregoing constitutes the preferred type of operating mechanism.

Referring specifically to our invention, there is an eccentric which operates a pitman 2| which passes through a rocking yoke 22 (Fig. 3). Yoke 22 is pivoted to the frame I by stud 23, which enables the yoke to rock as the pitman rocks from side to side A horizontal arm of the yoke has a. bore therethrough through which pitman 2| passes and is free to slide thereln- At the end of this horizontal arm opposite from pivot 23 there isa depending portion 24having a substantially vertical slot 25 therein. Passing through the slot is a stud 26 threaded into the frame I and fixed with respect thereto by means of a lock nut2l, the slot 25 enabling the portion 24 to slide with respect to the stud 26 as the yoke 22 rocks. The stud carries a nut 28 bearing against the rear surface of arm 24 and a nut. 29 hearing against the front face of arm 24. A lock nut 30 fixes nut 29 in position. It can be seen that by loosening lock nuts 21 and. 30 the stud 2'6. and nuts and 29 may be rotated to adjust the spacing of arm 24 from. the wall of frame I. In this manner the plane of parts perpendicularly fixed to the yoke 22 can be angularly shifted so that the position of the looper with respect to the needle 9 may be. accurately and easily adjusted and. fixed. Below the pivot 23 there is a vertically extending arm of yoke of pitman 2! is freely guided. Thus pitman 2| which'is a bore and in which the free lower end of pitman 2| is freely guided. Thus pitman 2| isguided to have a free vertical component; of movement and a restricted horizontal movement, which movement integrates into a closed path, described hereafter.

Fixed to the pitman, intermediatev of the two bores of yoke 22, is a block 38 having a forwardly extending lug. A double-armedlink 39 straddles this lug and is pivoted thereto by. means: of a tapering pin 40 which is longitudinally fixed by means of a set-screw 4|. The taper of the pin allows the mechanism to be tightened after it has become loosened due to the wearing away of the parts after long usage. Set-screw 4| allows the pin to be set in corrected position.

Extending forwardly from block 36 is a lug 42 having a threaded opening therein. An angular link 43 is pivoted to lug 42 by means of a threaded screw 44 having a long, tapered body, by means of which the wear in parts may be taken up. A small nut 45 looks screw 44 in adjusted position. The forward end of double-armed link 39 straddles link 43 at the apex of its angle and is pivoted thereto by means of a tapering pin 46 similar to pin 40, which pin is fixed in position by a set-screw 41 similar to set-screw 4i, and which allows wear at this point to be corrected.

The forwardly extending arm of link 43 carries the looper 50 which is attached thereto by means of a stud 5| passing into a bore in link 43 and which is locked in position by a set-screw 52. The stud 5| is flattened or grooved at the point of contact of set-screw 52 so that the looper is prevented from rotating with respect to the axis of pitman 2|. The looper has a longitudinal bore therethrough through which the looper thread 58 passes, and its lower end is tapered to a thin but rigid knife-like point. The looper thread passes through the bore in the looper and through a looper eye adjacent the point of the looper.

The parts of the looper have now been described with great particularity and the following will serve to explain its operation and the reasons for its peculiar advantages over the mechanism described in the copending application of Howland F. Briggs, heretofore mentioned.

It is essential and desirable that as high a speed of operation be obtained as possible. One of the uses to which the machine is placed is the automatic closing of filled bags as they are fed to the sewing machine from an. automatic bag filling machine. The speed of operation of the filling machine can be controlled and is solely limited by factors such as the speed of operation of the means for weighing and discharging a predetermined amount of material into each bag or the facility with which the operator is able to place bags in the filling mechanism. The speed of the filling machine has been increased. to a remarkable extent in machines such as disclosed in the copending application of Robert N. Cundall and Lincoln A. Cundall, Serial No. 688,816, filed September 9, 1933. In the operation of such machines it has been found that the largest number of failures is due to the dropping of stitches, or the formation of imperfect stitches, or the breaking of the stitching thread. The cause of such failures is primarily due to the inability of the previous type of looper to operate perfectly at the high speed of the machine. It was therefore found that the filling end of the machine had to operate slower than its normal operating speed, and hence at a reduced efficiency in order to allow the sewing mechanism to operate at its maximum efiiciency. Our present invention enables the entire machine to operate at a maximum speed.

The advantages of this invention are, first, that it makes certain that the needle will enter the so-called thread triangle created by the looper at its lowermost position, and secondly, that it makes certain that the looper will pick the needle thread from the needle in descending from its uppermost position. Perfection is insured by creating a longer period of dwell at the bottom of the looper stroke while giving the looper a broad horizontal sweep, and by causing the looper to ascend and descend in a rapid stroke having a very narrow horizontal range. The looper is thus caused to ascend rapidly while the needle is entering the work and to descend rapidly when the needle is fully thrust through the work, finely shaving the side of the needle on its downward stroke. Between the time that the needle is retracted from the work and again enters the work the looper is given very little vertical movement and a much greater horizontal movement so that a wider thread triangle may be created and held for a greater length of time. These movements result from the integration of the movements of various parts as will be apparent from the following description, having particular reference to Figs. 5, 6 and '7.

The center line of the eccentric 20 follows a true circular orbit about the center line of shaft 6. The free end of pitman 2| is slidably guided in the bores in yoke 22, and at or near a point E (Fig. 3) will have little or no horizontal component of motion, with the result that the free end of the pitman will always be travelling in the opposite horizontal direction from the upper end of the pitman. The resulting path of the point B (Fig. 1) is a vertical movement in simple harmonic motion, (Fig. 5) integrated with a varying horizontal movement to form the closed path illustrated in Fig. 6. This path is shaped like a conventional tear drop because the horizontal throw of point B is greater per degree of revolution, the farther point Bis from the pivot point E. The opposite end of link 39 is designated as C.

As point B travels upward, link 39 will be caused to tend to assume a vertical position, thereby causing link 43 to pivot about the tapered screw 44, and increasing the angle between links 43 and 39. The vertical path of point C is illustrated in Fig. 5. It can be seen that as the eccentric 20 rotates from 0 to of rotation, point C will not be given any vertical movement. From 40 to 60 there is a slight vertical movement, and from there on point C is raised and drawn toward the pitman in the manner indicated in Fig. 5. At the same time point C will be given a horizontal movement and this horizontal movement will be a true straight line from 0 to 40 since point C is not vertically shifted. As point B continues upward, point C is shifted horizontally, but to a lesser extent for each degree of rotation than from 0 to 40, as indicated in Fig. 6. Fig. 6 shows the resulting path of movement as projected on a vertical plane, i. e., the wall of the frame. The major vertical axis of this path is the total distance that point C is elevated, and the major horizontal axis of this path is the total distance that point C is shifted horizontally. It will be noted that the major horizontal axis of both of the paths described, are located at about 60 of rotation and that that of point C is longer than that of point B. The greater length is due to the fact that at 60 of rotation point C is farther away from point E, and hence has a greater horizontal throw.

The center line of the screw 44 is designated as point A. It will be appreciated that point A, during the entire cycle, is not given a vertical component of motion, but has a slightly curved substantially horizontal movement as indicated in Fig. 6, due to yoke 22 pivoting about stud 23. The horizontal throw of point A is greater than the horizontal axes of the paths previously decomponent of movement of point D imitates that of. points B. and C, and since the vertical distance from point E to point D is greater than the vertical distance from point E to point B for point C, the horizontal throw will be correspondingly increased so that the resulting path resembles that set forth in Fig. 6. The looper point-therefore remains at the same level from 0 to 40, and raises but slightly from 0 to 60, in fact receiving only about one quarter of its upward movement in the first 90 of rotation and. the other three quarters in the second 90 of rotation of shaft 6. From its uppermost point, the looper descends sharply and is given three quarters of its downward movement in the third 90 of a complete rotation of the shaft and the last quarter of its downward movement in the last 90 of rotation of the shaft.

In Fig. 6, the position and relative size of the needle has beenindicated. The needle 9 (Fig. 2) is provided with an eye 55 through which the needle thread 56 passes from the front of the machine, as indicated in Fig. 4. On the back of the needle there is usually and preferably provided a recess 51, so that the looper, in descending, will have ample opportunity to plckthe portion of needle thread 56 between the eye 55 and the material being sewed to form a loop which describes one side of the so-called thread triangle. It is for this reason that the point of looper 50 is formed into a very thin blade. With the previous type of looper, even though the recess in the needle were used, occasionally the needle thread was not stripped off by the looper. With our device the sharp, quick, downward stroke of the looper insures its entry into recess 51 and the removal of the needle thread. It can be seenthat the fine degree of adjustment of the looper relative to the center line of the needle, provided by adjusting stud 26, affords accurate driving of the point of the looper into the recess 51, and the rigidity of the mechanism prevents disalignment even with an unusual amount of machine vibrations. Likewise, it is apparent that the long dwell of the looper, together with the large horizontal component of motion at the bot tom of its stroke, insures the correct tightening of the previous stitch, as well as the formation and maintenance of a broad thread triangle as indicated in Fig. 6. Fig. 6 shows the thread loop stripped off from the needle at the previous stitch as it is held around the looper in its upward motion, and as the needle is penetrating the thread triangle formed by the thread loop of the needle thread 56, and the looper and looper thread 58.

. The capability of the device to form and hold a large triangularis apparent. It will-be appreciated that a further advantage to the device occasioned by the great horizontal movement, is

that as the looper is travelling horizontally at its.

lowermost position, the previously formed stitch can be drawn very tightly, the degree of tension desired being regulated by thread tension devices, such as schematically represented in Fig. 4. The tightness of the stitch can be maintained, since'the material is fed forward as the looper travels. from its lowermost position to a slightly elevated position, thereby holding the long'legs of the thread triangle at practically'constant lengths.

Figs. 6 and '7 show a feature of my device as set up inthepreferred embodiment. In these figures XX represents the true vertical or a line parallel to the major vertical axis of the machine and the line E, B represents the longitudinal axis of the eccentric 2|. It is therefore seen that the center line of the stud 23 is substantially verticallybelow the axisof rotation of the eccentric 20. Fig. 7 diagrammatically represents the position of pitman 2| at 0, 90, 18 and 270 showing that the pitman is closest to being vertical at 270? of rotation during the downward stroke thereof. As a result the downward stroke of the looper' is closest to the vertical and the triangular path of the looper is canted. with respect to the vertical, having one of the equal legs thereof substantially vertical and the smallest angle thereof uppermost. The advantages flowing from this arrangement are primarily that the downward stroke of the looper may be more accurately adjusted with respect to the needle and there will be less likelihood of stitches being dropped, and the horizontal movement of the looper extends farther to the right of the needle therebydrawing through the center line of the stud 23; The

result occasioned bythis is that the ends of the paths defined by points B and C and the upper end of the path defined by point D, are not sharp rectilinear angles but are slightly curved, or parabolic, in outline. The offsetting of point E with respect to the pivot 23 enables the arcuate adjustment of the looper about the pitman 2| as previously described.

Having described our device with-such particularity that it may be readily understood, we nowclaim as our invention the specific embodiment as" well as such modifications and alterations thereof. as come within. the scope of the following claims, which are to be broadly construed.

We claim:

1. In a sewing machine employinga reciprocat-- ing needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pitman driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, the length of the base of the triangle being approximately one half of the length of. the legs of thetriangle.

2. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form thread loops, at driving shaft to operate said needle and looper, a pitman driven from said driving shaft, and means connected to said pitman and said looper to cause said looper to traverse a closed path substantially triangular in. outline, said single pitman being the sole connection between said looper and said driving shaft to cause said looper to traverse the path described.

3. In a sewing machine for forming av double thread interlocked chain stitch, a needle adapted to carry'a thread and to be reciprocally moved to pierce the material being sewn with saidthread at stitching intervals, a looper adapted. to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, and a member slidably guiding said pitman, said looper being supported by a toggle connected to said block and said member.

4. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, and a member slidably guiding said pitman, said looper being supported by a toggle connected to said block and said member, and said member being supported to rock about a fixed point.

5. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, a member slidably guiding said pitman, said looper being supported by a toggle connected to said block and said member, and tapered pins connecting the links of said toggle to each other and to said block and said member. 6. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, a member slidably guiding said pitman, said looper being supported by a toggle connected to said block and said member, and means to adjust said looper arcuately about said pitman.

'7. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, and a pivotally mounted yoke slidably guiding said pitman, said looper being supported by a toggle connected to said block and to one of the arms of said yoke.

8. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, a pivotally mounted yoke slidably guiding said pitman, said looper being supported by a toggle connected to said block and to one of the arms of said yoke, and means associated with one of the arms of said yoke to adjust said looper arcuately about said pitman.

9. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a tlnead and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, 9. looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, a pivotally mounted yoke slidably guiding said pitman, said looper being supported by a toggle connected to said block and to one of the arms of said yoke, and means associated with one of the arms of said yoke to adjust said looper arcuately about said pitman, said means comprising a stud passing through a slot in the associated arm of the yoke.

10. In a sewing machine for forming a double thread interlocked chain stitch, a needle adapted to carry a thread and to be reciprocally moved to pierce the material being sewn with said thread at stitching intervals, a looper adapted to carry a second thread, an eccentric and pitman operating said looper, a block fixed to said pitman, a pivotally mounted yoke slidably guiding said pitman, said looper being supported by a toggle connected to said block and to one of the arms of said yoke, and means associated with one of the arms of said yoke to adjust said looper arcuately about said pitman, said means comprising a stud passing through a slot in the associated arm of the yoke and adjusting nuts on said stud at each side of the arm.

11. In a sewing machine employing a reciproeating needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pitman driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle.

12. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pitman driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, the length of the base of the triangle being approximately one half of the length of the legs of the triangle, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle.

13. In a sewing machine employing a reciproeating needle, a looper cooperating with said needle to form thread loops, a driving shaft to operate said needle and looper, a pitman driven from said driving shaft, and means connected to said pitman and said looper to cause said looper to traverse a closed path substantially triangular in outline, said single pitman being the sole connection between said looper and said driving shaft to cause said looper to traverse the path described, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle.

14. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pitman driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, said pitman being canted with respect to the vertical whereby the triangular path described is canted with respect to a normal to the line of stitches being formed.

15. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pit man driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, the length of the base of the triangle being approximately one half of the length of the legs of the triangle, said pitman being canted with respect to the vertical whereby the triangular path described is canted Withrespect to a normal to the line of stitches being formed.

16. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form threadloops, a driving shaft to operate said needle and looper, a pitman driven from said driving shaft, and means connected to said pitman and said looper to cause said looper to traverse a closed path substantially triangular in outline, said single pitman being the sole connection between said looper and said driving shaft to cause said looper to traverse the path described, said pitman being canted with respect to the vertical whereby the triangular path described is canted with respect to a normal to the line of stitches being formed.

17. In a sewing machine employing a recipro-- cating needle, a looper cooperating with said needle to form thread loops, a drive shaft and a pitman driven thereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle, said pitman being canted with respect to the vertical whereby the triangular path described is canted with respect to a normal to the line of stitches being formed.

18. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to formthread loops, a drive shaft and a pitman driventhereby, and means connected to said pitman and said looper to cause said looper to traverse a substantially triangular path, the length of the base of the triangle being approximately one half of the length of the legs of the triangle, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle, said pitman being canted with respect to the vertical whereby the triangular path described is canted with respect to a normal to the line of stitches being formed.

19. In a sewing machine employing a reciprocating needle, a looper cooperating with said needle to form thread loops, a driving shaft to operate said needle and looper, a pitmandriven from said driving shaft, and means connected to said pitman and said looper to cause said looper to traverse a closed path substantially triangular in outline, said single pitman being the sole connection between said looper and said driving shaft to cause said looper to traverse the path described, said means causing said looper to traverse the path described at a varying rate of speed, the speed being relatively slow across the base of the triangle and fast along the legs of the triangle, said pitman being canted with respect to the vertical whereby the triangular path described is canted with respect to a normal to the line of stitches being formed.

I-IOWLAND F. BRIGGS. ROBERT N. CUNDALL.

CERTIFICATE OF CORRECTION.

Patent No. 2,079,062. May 4;, 1957.

HOWLAND F. BRIGGS, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, lines 44-45, for of pitman 21 is freely guided. Thus pitman 21 which is a bore and in which the free lower end" read 22 which has a block 36 attached thereto through which is a bore and in which the free lower end; page 3, first column, line 12, for "for read or; and second column, line 14, for "18" read 180 and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of July, A. D. 1957.

Henry Van Arsdale (Seal) Acting Commissioner of Patents, 1 

